Tabulation and margin control structure

ABSTRACT

A tabulation and margin control structure for use with a character-by-character printer having a margin stop rack and a tab rack each supported for pivotal and longitudinal motion away from a home position. In response to a start tab signal, the tab rack is pivoted to rotate tab stop members into engaging relationship with a tab pawl member and in response to the pivotal motion of the tab rack, an escapement pawl is extracted from the engaged rack tooth to allow carrier motion. In response to the engagement of the tab pawl member with a tab stop, the tab rack is moved longitudinally and produces an electrical signal which initiates a reverse pivotal motion of the tab rack to terminate tab motion and reengage the escapement pawl with the associated rack. In response to the carrier entering a zone defined by the position of the right-hand margin stop member, the margin stop rack is pivoted and an electrical signal provided indicative of entry into the zone. In response to a carrier return signal, the carrier is moved to the left until a projection on the carrier engages the left-hand margin stop member, thereby moving the margin stop rack longitudinally. In response to said last mentioned longitudinal motion, an electrical signal is generated to terminate the carrier return motion.

United States Patent [72] Inventors Donald L. Rolph Fairport; Ronald Trista-am, Rochester, N.Y. [21] AppLNo. 673,440 [22] Filed Oct. 6, 1967 [45] Patented Jan 12,1971 [73] Assignee The Singer Company a corporation of New Jersey [54] TABULATION AND MARGIN CONTROL STRUCTURE 6 Claims, 7 Drawing Figs.

[52] U.S.Cl 197/176, 197/63, 197/70, 197/94 [51] 1nt.Cl B4lj25/l8 [50] FieldofSearch ..197/63,64, 70, 92, 94, 96, 176, 176a, 177, 178, 179

[56] References Cited UNITED STATES PATENTS 1,021,391 3/1912 Waldheim 197/177 1,193,073 8/1916 Roebuck..... 197/176 1,544,240 6/1925 Kurowski.... 197/176 2,160,254 5/1939 Smith l97/70X 2,225,450 12/1940 vHelmond 197/178 2,372,886 4/1945 Dodge 197/178 RE23,834 6/1954 Rainey..... 197/70 3,037,606 6/1962 Blain et a1 l97/70X 3,346,091 10/1967 Cralleetal. 3,429,415 2/1969 Hirata Primary Examiner-Ernest T. Wright, Jr. Attorneys-George W. Killian, Patrick .1, Schesinger, Charles R. Lepchinsky and Jay M. Cantor ABSTRACT: A tabulation and margin control structure for use with a character-by-character printer having a margin stop rack and a tab rack each supported for pivotal and longitudinal motion away from a home position. In response to a start tab signal, the tab rack is pivoted to rotate tab stop members into engaging relationship with a tab pawl member and in response to the pivotal motion of the tab rack, an escapement pawl is extracted from,the engaged rack tooth to allow carrier motion. ln response to the engagement of the tab pawl member with a tab stop, the tab rack is moved longitudinally and produces an electrical signal which initiates a reverse pivotal motion of the tab rack to terminate tab motion and reengage the escapement pawl with the associated rack. in response to the carrier entering a zone defined by the position of the right-hand margin stop member, the margin stop rack is pivoted and an electrical signal provided indicative of entry into the zone. In response to a carrier return signal, the carrier is moved to the left until a projection on the carrier engages the left-hand margin stop member, thereby moving the margin stop rack longitudinally. In response to said last mentioned longitudinal motion, an electrical signal is generated to terminate the carrier return motion.

PATENTEU JANIZIHYI 35541350 sum lflF 4 0% 27m mLaN M 2m own 5 2m. an

S n 0 m2 M 5m Q 5 E E V E I w 1 E E H II DONALD L. ROLPH RONALD TRISTRAM AGENT PATENTED m 1 2 |97| SHEET 2 BF 4 PATENTEI] JA 1 IBYI SHEET 3 BF 4 PATENTED JAN 1 2197:

SHEET '4 OF 4 r CNN Q2 mm Na 3 1 TABULATION AND MARGIN CONTROL STRUCTURE The present invention relates to serial character page printers and, more specifically, to power-operated printers which respond to data presented in coded form and automatically prints such data in serial character orm at desirably high printing rates, and even more particularly, to a tabulation and margin control structure and electrical control system therefor. Many forms of tabulation and margin control structure have been employed in the ubiquitous manual and electric typewriters.

Printers which print in response to human control are seldom required to print at a rate faster than approximately 12 to 15 characters per second and then .only for a brief period. However, as printers were developed which were capable of responding to input coded signals and printing at much higher printing rates it became necessary to develop improved tabulation and margin control structures which could provide the necessary relative motion between the document and the printing elements at the necessary speed.

In copending application Ser. No. 630,904, filed Apr. l4, 1967, now US. Pat. No. 3,426,880 by Edwin O. Blodgett, and assigned to the sameassignee as the present application, there is, disclosed the complete details of a high speed serial character matrix page printer which is capable of printing at a much higher sustained printing rate than the conventional manual or electric typewriters. The tabulation and margin control structure disclosed and claimed herein is suitable for use withthe printer disclosedrin the cited copending application, and/or with other printers which may be required to print on a character-by-character basisand/or with printers having a wide range of printing speeds.

Prior art tabulation and margin control structures have been perfectly satisfactory for use with printers that responded to manual input. However, the prior art devices exhibited a variety of faults when used with high speed printers. For example prior art techniques tended to be so slow that when used with high speed printing techniques a significant amount of time was expended in tabulation, thereby resulting in an equivalent reduction in printing speed. The simple and obvious expedient of using stronger springs or other driving forces to obtain faster tabulation created difficulties; not the least of which was the additional shock transmitted to the system and an increased tendency for the carrier to bounce after hitting the stop, thereby resulting in the'ultimate positioning of the carrier at a different position from that which is desired. That is, the carrier might bounce one or more full character units away from the stop and be held in the wrong position by the escapement mechanism.

Accordingly, it is a principle object of this invention to provide a new and improved tabulation and margin control structure.

It is a more specific object to provide a new and improved tabulation and margin control structure for use with a high speed character-by-character printer.

It is another object of this invention to provide a tabulation and margin control structure which comprises a minimum number of parts and which is easy to assemble and adjust.

It is a more particular object of this invention to provide a tabulation and margin control structure for providing rapid and accurate tabulation control.

It is another object of this invention to provide a tabulation control action which is initiated in response to an electrical signal and which produces an electrical signal at the conclusion of the tabulation action.

It is another object of the invention to'provide a margin control system wherein an electrical signal is generated when the right-hand margin is approached.

It is another object of the invention to provide a margin control system'which produces an electrical signal indicative of the carrier having been restored to the left-hand margin position. In accordance with this invention there is provided a tabulation rack and margin stop rack both of which are biased to home positions and both of which may be independently moved from said home position by either or both pivotal or longitudinal motion.

Other objects, features, and advantages of the present invention will appear as a detailed description thereof proceeds in the light of the drawing forming a part'of this application and in which:

FIG. 1 illustrates in plan view the construction of the letter escapement structure, parts of the tabulation structure and margin control structure utilized in a printer for effecting letter escapement spacing, tabular motion and margin control between the print head carrier and the platen;

FIG. 2 illustrates additional details'of the carrier, the tabulation rack and the margin control;

FIG. 3 illustrates in plan viewthe carrier support and its cooperative arrangement with the letter spacing structure and the horizontal tabulation and paper margin structure included in the printer;

FIGS. 4-6 in conjunction with FIGS. 1 and 3 illustrate the novel horizontal tabulation structure and the novel paper margin control structure employed in the printer with FIG. 4 being taken along section line 4-4 of FIG. 3 and FIG. 6 taken along section line 6-6 of FIG. 4; and

FIG. 7 shows the construction of the carrier utilized in the printer.

To aid the reader who may be interested in obtaining more details concerning the printer in which the present invention is illustrated, the above-identified FIGS. are identical to some of those in the cited Blodgett application. More specifically, FIGS. 1-7 in the present application correspond to FIGS. 15, 10, 12, l7, 16, 18, and 9, respectively, of the cited Blodgett application. For convenience, identical reference numbers are used in the present application and the cited Blodgett application.

The tabulation structure includes a tab rack 280 which, as shown in FIG. 3, is provided with cylindrical end portions 281 and 282. The end portion 281 is supported for longitudinal displacement and pivotal motion by a journal aperture provided in one forwardly projecting arm 283 of the cast pedestal 27, and has a fixed radial pin 284 slidably received in a longitudinal slot 285 provided at the end of the rotary shaft 286 of a rotary electromagnet 287 supported on a second arm 288 of the cast pedestal 27. The end portion 282 of the tab rack 280 is similarly supported for longitudinal displacement and pivotal motion by an aperture provided in the cast pedestal 29. A collar 289 secured on the'end portion 282 anchors one end of a helical spring 290 having its other end anchored by the cast pedestal 29 to bias the tab rack 280 to the left as seen in FIG. 3 and pivoted to thedeenergized stop position of the electromagnet 287 at which position the tub rack 280 occupies the angular position shown in FIG. 2. A collar 29] affixed to the end portion 282 of the tab rack 280 carries an am 292 which at either of two tab rack angular positions, shown infull and broken lines in FIG. 5 corresponding to the deenergized and energized state of the rotary electromagnet 287, operates a microswitch 293 supported on an integral laterally extending flange 294 of the cast pedestal 29.

Conventional tab stop members 295 are manually positioned on the tab rack 280 at preselected tab positions as defined by conventional slide slots 296 of the tab rack-280i A tab pawl member 297 is pivotally supported, as shown more clearly in FIGS. 1, 2, and 7, on a bracket 298 secured by machine screws 2990n a radially extending flange300KFlG. 2) of the left-hand cast flange 151 as seen in FIGS. 1 and 3,-the pawl member 297 being biased by a spring 301 normally to-engage a dependent stop portion 302 of the bracket 2 98". The deenergized state of the rotary electromagnet 287 angularly positions the tab rack 280 as shown in .FIG. 2 at which the pawl member 297 normally does not engage. the tab stop members 295 during movement of the carrier a longitudinally along the rail 153.

A tab function codesupplied to the printer is decodedby a decoder unit of the printer electrical control system more fully described in the cited Blodgett application and effects energization of the rotary electromagnet 287 to pivot the tab rack 280 through a small counterclockwise angle as seen in FIG. 2 and thus positions the tab stop members 295 in engageable relation with the tab pawl member 297. At the same time, the tab code effects deenergization of an electromagnet of a last character visibility structure more fully described in the cited copending Blodgett application, and this structure rotates the eccentric shaft 159 to its position shown in broken lines in FIG. 2 to pivot the carrier 2 through a small counterclockwise angle as seen in FIG. 2. That is, the carrier is pivoted on rail 153 which passes through apertures 152 of flanges 151 and the pivoting motion is transmitted from shaft 159 through yoke 157 which is secured to arm 156 by screw 158. This pivoted position of the carrier Z2 and the pivoted position of the tab rack 280 effected by energization of the rotary electromagnet 287 engages a roller 303 with a track strip 304 secured along the lower surface of the tab rack 280 as shown. The roller 303 is rotationally supported by a stud 305 provided on the overturned ends 306 (FIG. 1) of a lever 307 pivotally secured at 308 on the escapement bracket 261 and has an upturned end 309 which engages the rear edge of the pawl 266 to withdraw the pawl nose portion 271 from engagement with the rack teeth 272 upon pivotal motion of the lever 307 by engagement of the roller 303 with the track strip 304. This enables the carrier E to be spring motor driven in a direction from left to right of the printer platen (not shown) until the tab pawl member 297 engages one of the tab stop members 295 on the tab rack 280. When such engagement occurs, the tab rack 2805s moved longitudinally to the right (FIG. 3) against the compressive force of the spring 290 and through the arm 292 operates the microswitch 293 to deenergize the rotary electromagnet 287. Such deenergization permits the rotational bias force of the spring 290 to pivot the tab rack 280 to the position shown in FIG. 2. This permits the pawl spring 270 once more to move the pawl nose portion 271 to a position where it can engage the next succeeding rack tooth 272 of the rail 153. The disengagement of the pawl member 297 with tab stop 295 permits the carrier 31 to move a character space to the right as controlled by the earlier described engagement of the pawl nose portion 271 with the next succeeding rack tooth 272 of the rail 153 under bias of the pawl spring 270, thus completing the tabulation operation. (More complete details of the letter escaping mechanism may be seen in the cited copending Blodgett application and/or in the copending application of Henry E. Smith, Ser. No. 666,583, filed Sept. l l, l967, and assigned to the same assignee as the present application.) If the rotary electromagnet 287 should remain energized during the power driven movement of the carrier from the right margin position to the left margin position of the platen (not shown), a cam surface 310 (FIG. 1) of the tab pawl member 297 pivots this member 297 counterclockwise to permit passage of the tab pawl member 297 past the tab stop members 295.

During normal printer action when the carrier 31 reaches the right-hand margin stop 322, an electrical signal is generated which defines the start of a printing zone within which a carrier return operation takes place. Within this zone, the printer continues printing and character spacing successive alphanumeric characters, symbols, and punctuation until the next word space code is received, whereupon the carrier 2 is rapidly power driven until it engages the left-hand margin stop 318. This zone character of carrier return operation prevents interruption of printing before the entire last word of the line has been printed. The novel structure and electrical system for accomplishing such zone character of carrier return from right to left of the printer platen is shown and claimed in copending application of David. W. Engdahl, Ser. No. 702,305, filed Feb. l, I968, and assigned to the same assignee as the present application. The margin control structure is shown in plan view in FIG. 3 and is shown in more detail in FIGS. 1. 2, and 46. It includes a margin stop rack 315 having a cylindrical end portions 316 and 317 supported for longitudinal displacement to the left as seen in FIG. 3 and for pivotal motion by journal apertures provided in the respective cast pedestals 27 and 29, which also has apertures 154 for supporting rail 153 which is held in position by set screws 155. A conventional left-hand margin stop member 318, biased by a leaf spring 319 (FIG. 1), to engage internal teeth 320 with edge slots 321 of the rack 315, may be manually depressed for setting at any desired left-hand margin stop position. A similar right-hand margin zone control member 322 may be manually set at any desired right-hand marginal control position. One side of the stop control member 322 has an integral boss 323 (FIG. 2) having a stud 324 upon which a roller 325 is rotationally supported and retained in position by a C-spring 326. The margin stop rack 315 is biased to the right as seen in FIGS. 3 and 4 by a compression spring 327 positioned between the cast pedestal 29 and a collar 328 secured by a set screw 329 on the cylindrical portion 317; but its right-hand at rest position is fixed by a pin 330 projecting through and secured to the cylindrical portion 317 and which engages a flanged bushing 331 seated in an aperture 332 of the cast pedestal 29 as shown. Longitudinal displacement of the stop rack 315 to the left (as seen in FIG. 3) from its at rest position is permitted by compression of a washer 333 of an elastomer material positioned between a boss 334 on a pedestal 27 and a collar 335 secured on the cylindrical end portion 316 of the stop rack 315. The righthand end of the cylindrical end portion 317 has an internally threaded axial bore receiving a flatheaded machine screw 336, shown more clearly in FIG. 4, which in the at rest position of the stop rack 315 operatively engages a microswitch 337 supported upon an upstanding flange 338 of an L-shaped bracket 339 cast on the side of the pedestal 29 as shown.

As illustrated in FIGS. 1, 2, and 3, the left-hand flange 151 of the carrier 12 has an integral projection 340 which during power drive movement of the carrier to the left engages the left-hand margin stop 318 and displaces the stop rack 315 to the left. This displacement operates the microswitch 337 which is included in an electrical control circuit described more fully in the cited Blodgett application and effects termination of the power drive of the carrier E The right-hand flange 151 of the carrier E is provided with a projecting nose member 341 which, during spring motor print escapement of the carrier 77 to the right, or during tabular motion to the right, engag es the roller 325 on the right-hand margin stop control member 322 and thereby pivots the margin stop rack 315 about the axis of its end portions 316 and 317 but without longitudinal displacement of the stop rack 315 to the right since such movement is restrained by the pin 330 of the end cylindrical portion 317. Thus, pivotal motion of the stop rack 315 effects corresponding rotational movement of the collar 328 (FIGS. 4-6). A platform 342 has an upturned side flange 343 which is extended upwardly and is secured to the collar 328, and has a further upturned side flange 344 having a downwardly extending arm 345 which anchors one end of a tension spring 346. The latter has its opposite end anchored by a stud 347 carried by the bracket 339 and biases the platform 342 to a position engaging the end of an adjusting screw 348 threaded through the bracket 339. The position of the platform 342 as established by the set screw 348 places the platform 342 in an operative engagement with a microswitch 349 supported on the bracket 339 and also by the connection of the platform flange 343 to the collar 328 establishes the at rest angular position of the marginal rack 315. When the latter is rotated by engagement of the carrier nose member 341 with the roller 325 of the righthand margin stop control member 322, the platform 342 is angularly displaced to operate the microswitch 349 which is included in an electrical control circuit described more fully in the cited Blodgett application and causes the next received word space code to effect power driven return movement of the carrier Z1 to the left-hand margin gogition as established by the left-hand margin stop member Asalluded to. hereinabove and.-as.more fullydescribed in the, cited copending application of Blodgett-s, the. carrierv structure, E includesan escapementmechanism'which will b herein described brieflyas it cooperates withthetabulationstructure forterminatinga tabular motion. The.escapementstructure includes an arm. 252 securedupon theupper end of theright harrl one of the two shafts- 210 :asshown in' FIG, 7jand, which islzangplarly reciprocated as more fully ex plained; in. the copending cited Blodgettapplication to reci ocate thepressure plate,205-between nonprint and print positions. duringeachprint operationvA Oshaped slotted end .1 portion. 25.4lof. arm 2s'receives the end ,of= an L-shaped; 255 ;havingan, elongated slot25 6wby which it is supported fori. longitudinal pivotal ,and reciprocal motion on the shaft 210. Bias; spring;.258 --anchore1;l atnone. end, by a pedestal. 259 mounted uponithe. baseportion 260.; biases am {255 1 to; the rightasviewedv in.FIG 1. The escapement pawl. 26.6;is pro-r vided,; with an elongatedlaperture.2671by whiehit is mounted 5 motor drive 249. and cable-246connected to carrier 6% 23.4 secured to-the. bracket 'l66 and'a diametrically opposed-J hook end. portion 235.0fthe arm 92.

The print .head carrier (FIG. 7) duringaprintin'gof successive 'charactersof a line of copy" is.-urged; by spring:

77 to. move in -a direction from left" to right ofthe printer -platen. (not shown), and. upon'completing'a line of 'copy,.is-rapidly driven in theopposite direction. This;bidirectional drive mo tion of'the'carrier is-accomplished by-adrive strue-'- ture more fully disclosed in the.citedtpendingapplicationofE; O. Blodgett and isshown' schematically in FIG. Thereinsascomprisedby thecable 246lwhich is connected 'by a yoke-247 tor. the. carrier base casting a 1503 extends' 'over an== idlerspulley 2.48;;is;wrapped about'the spring'motor drive'249 supported upon a drive shaft.25.0; extends ovenan idle'rpulley 251 and-is secured to the: carrier: brackete l66: as -shown; Th'espaced pointsoflwhich theends ofathecable 246 are'c0nn'ectedtothe carrierstructure; lieon a-planeparalleltothe'axisof pqnl el tu 5 m is e r n p i i n th re n by-a C- 20 the rail.l53 so;thattdrive forces exerted. by the cable lz46lhave.

spring2 68r Asshownrnore clearly in FIG. 1, thepawl 26,6 hasv an apertured.sideprojecting portion 269. anchoring one end-of; a tension spring. .270 which is anchored at its; opposite endon p thepedestal ,259eand. by=,which;the pawl 26 6 lis, biased to the.

no tendency to-.twist orlrock thecarri'er 153.

The. character seleetionplatei 85is displaced verticall y and horizontally for: character selection. To this end Jthenselectiona on the rail right aS- enliniFl s' T p l 61 ;1 m':'273fWhiCh j 5- plate;85:=-has a turned-over ear 86- whichlengages a verticalmay engagetheupturned endportion of .thearm 2553-:-

Theprint head is of the wire printer .typeandincludesafum nel housing .178 ofgU-shaped transverse cross. section .open. at the. bottom andwhi c h isaffixed by brazing vorsolderto a.-,plate 179 secured by machine. screws 1 80,-to a mounting plate-181,; The latter islpositio ned in the central rectangularaperture149%. of ,the;-.base,.casting..150 :and .is provided ,with 1endl-flanges'tl82i which; are seeuredlto the-base casting.lsfl by machinescrewsl83;- As morefully. describedin the;cited.eopending-Blodgett.

groove STOfrthfi-PiStOl'l 8-2Tguidedwithina cylinder 83 to permit:vertical..-displacement of the-"plate. 85"%withrespect to th'e r piston 1821; andz'has. side positioned. turned-ovenears' 88 i which' arezengagedby end:grooves=89 of a positioning arm' 90--verti- 1 cally guidedon a guide rodz.9l .carried:by thecarrier-structure and-vertically.moved by apivoted be]lcrank 92 mechaniscally coupled tothearm90'ibya=link:member93i 1 While there .has' been shown and: described :what is considered at present to besthes-preferred embodiment of .tlre'in pp i a ion-Aha a tu lprintingi n by e st f p li y 5 vention; modifications-theretowill readily: occur. to those:

of print .wireswhichextend th-roughnose block-1892 :T he. print wires. areprojected ,to their printinggposition byaa. character: selectionplate 85;-and withdrawn from. the, printing position bya stripper. plate. 195; The characterselection plate: 85 is driven ;,4

to print position by spring. 2l8vwhen the-tension l in cable-.220.

whichfi S-l anchored .by yoke. 1221- is relaxed. The stripper plate.

195 has: upper and lower pairs of forwardly: extending. arms 202 by. which it is supported upon, and reciprocally. moved by. an upper rod 203:.anda lowerrod'204rArmsn2omof'pressure plate. 2il5- are also supported upon, the. rods 203. and 204. -Also supported upon the rods 203 .are apair of metal blocks 20'll whicharepivotally connectedgto the end of individualones of a pair of arms 2091 =secured at the upper-endsof apainof spaced. shafts 210: rotatablyl joumaled,- as shown in. FIG. 7,by-

the-brackets 166 amass. The-shafts 210 areprovided with oil 5 felt washers 21 land areretained in position by Gsprings 212;; The: lowerrod 204zsimilarly supports, metal. blocks 213.which' are pivotally connected. to arms,214 secured, on 1thetlower;

ends of. the shafts 210 In'thel middleof each. shaft.210..is an arm 2l4 the ends of which'arepivotally connectedby a link member .2 l5,for angular rotation;-in,t1nison.,The; leftshand. one: of theshafts 210 as seen. in FIG. 7 also. has-secured thereto an arm- 216 ='(FlG. 2) havingan-extended .portion 2171,(P:lG.'.7)

and a tension spring; 2l8 anchored .between theizann; portions 0 217 and..a .U-shaped staple. 2l9 ;secured to thel-bracketzl66a. biasing .theshaft 210 f0r counterclockwiserotations The character selection; .plate. 85 is retained in slidable; en gagementswith the pressure plate 205; by spaced; flanges 238i extending from. thestripper plate; 195140. engage the adjaeentzbj surface of; theeharacter [selection plate; 85: The horizontal. selection platepositioning band.76shas Ol'ICgCIld,SCCUl'd-; to the. l. print. head carrier structure and its other. end secured. to, thelpiston 82.;More particularly, as seen in;FIG. 7;

a yoke. 225;;is, secured. to each end of the=,band,;76"'and;the: remote end of.the yoke.2 25"has apin 226-securedbetweenrthe; f

arms .offlyoke 2259to engage a hook 1 member c227. isecured to the bracket;166.and;adiametrically opposedhooklend portionu 228 ofthelpiston182 The ends of; .thelbandl94 -haveyokes 232;?

secured theretoand yoke .endipins 233 engagea hook rn er nber skilled in theart: It isnot desired,ltherefore; that'tlie inventionbe-limited :to the. embodiment shown and' described; and itis intended "to'cover in the appended claimsralll-such modifica O tions-as fall within thetruespirit and scopeiof the inventionz first means forpivoting said tab'rack awayfrom said homer? position of said tabrrack forextracting-saidfirst pawl means frbm's theengagedroneof said: 'rackteeth'of said support'raikli said second bias means :moving: said carrier means withsaidi'i letter spacing motion l in responseto theextracti'on of t'n'st-pawlmeans; Saidasecond: pawl means engagingtsaid tabistop member r" response to the *letten spacing I motionr of' said carrieri means;

said,.=tab:track beingamoved-.alongitudinally==away.a-frornr' said homespositionnby the force "of saidvsecond biasmean's aftersaid secondrpawl means :has engaged-ssaidtab stopsmember;

said first; means. being :responsivetocthe longitudihal tnotion r-:

of saidutab rackufor -.pivotingrsaid\:tab rack'ab'ack to" said"? homerpositionyandu first bias means -foriurgingrsaid. tabf rac k towardslsaid-home pawl'extracting means responsivertothe=said=ipivotal inotionn third bias means responsive to the pivoting of said tab rack back to its home position for pivoting said first pawl means into engagement with one of said rack teeth of said support rail for terminating the letter spacing motion of said carrier means.

2. The combination as set forth in claim 1 wherein said pawl extracting means COPDI'lSCS a linkage mounted on said carrier means and having a first end for engaging said first pawl means to extract said first pawl means from the engaged rack tooth of said support rail, and having a second end for sensing when said tab rack is pivoted away from said home position.

3. The combination as set forth in claim 2 wherein said linkage comprises a single assembly pivoted intermediate its ends on said carrier means.

4. The combination as set forth in claim 2 wherein said tab rack includes a planar surface for engaging said second end of said linkage in response to the pivoting of said tab rack away from its home position.

5. The combination as set forth in claim 1 wherein said first means comprises a rotary electromagnet.

6. The combination as set forth in claim 5 and including electrical contact means responsive to the longitudinal motion of said tab rack away from its home position for providing an electrical signal to said rotary electromagnet for pivoting said tab rack back to its home position. 

1. A tabulation assembly comprising: a tab rack supported for pivotal and longitudinal motion away from a home position; first bias means for urging said tab rack towards said home position; a tab stop member mounted on said tab rack; a support rail having rack teeth and supported in a position parallel to the longitudinal direction of said tab rack; carrier means mounted on said support rail for letter spacing motion relative to and parallel to said tab rack; second bias means for urging said carrier means in a letter space direction; first pawl means mounted on said carrier means for engaging one of said rack teeth of said support rail to inhibit the letter spacing motion of said carrier means; second pawl means mounted on said carrier means; first means for pivoting said tab rack away from said home position; pawl extracting means responsive to the said pivotal motion of said tab rack for extracting said first pawl means from the engaged one of said rack teeth of said support rail; said second bias means moving said carrier means with said letter spacing motion in response to the extraction of said first pawl means; said second pawl means engaging said tab stop member in response to the letter spacing motion of said carrier means; said tab rack being moved longitudinally away from said home position by the force of said second bias means after said second pawl means has engaged said tab stop member; said first means being responsive to the longitudinal motion of said tab rack for pivoting said tab rack back to said home position; and third bias means responsive to the pivoting of said tab rack back to its home position for pivoting said first pawl means into engagement with one of said rack teeth of said support rail for terminating the letter spacing motion of said carrier means.
 2. The combination as set fortH in claim 1 wherein said pawl extracting means comprises a linkage mounted on said carrier means and having a first end for engaging said first pawl means to extract said first pawl means from the engaged rack tooth of said support rail, and having a second end for sensing when said tab rack is pivoted away from said home position.
 3. The combination as set forth in claim 2 wherein said linkage comprises a single assembly pivoted intermediate its ends on said carrier means.
 4. The combination as set forth in claim 2 wherein said tab rack includes a planar surface for engaging said second end of said linkage in response to the pivoting of said tab rack away from its home position.
 5. The combination as set forth in claim 1 wherein said first means comprises a rotary electromagnet.
 6. The combination as set forth in claim 5 and including electrical contact means responsive to the longitudinal motion of said tab rack away from its home position for providing an electrical signal to said rotary electromagnet for pivoting said tab rack back to its home position. 